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Experimental Investigation ofClosed-loop Pulsating Heat-pipe with an Additional Branch in the Evaporator Section

Sedighi, Erfan | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50383 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. The main idea of this investigation is to increase heat transfer rate by increasing flow circulation of working fluid. By placing additional branches in the evaporator section, secondary bubble pumps were created which improved the circulation of fluid inside PHP. This research was implemented in two distinct phases. In the first phase, the novelty was implemented on a single turn PHP and in the second phase, the same procedure was implemented on a 4-turn PHP. In order to investigate the impact of these additional branches, two similar heat pipes were fabricated. One of them was the conventional PHP and the other had additional branches and is named additional branch PHP (AB-PHP). Thermal performances of these two types of heat pipes were investigated at different filling ratios, inclination angles (just in the first phase) and heat inputs. Results of the first phase showed that the thermal performance of the AB-PHP is considerably better than the conventional PHP in the vertical orientation using filling ratios of 40 % and 70 %. Furthermore, comparing the performance of these two systems at the optimum filling ratio (60 %) and different inclination angles indicated the better performance of AB-PHP in non-vertical positions including horizontal position. To better understand the effect of the additional branch in the AB -PHP, a Pyrex heat pipe similar to the copper type was fabricated and the flow circulation was visually analyzed. Results of the second phase showed that the thermal performance of the AB-FP-PHP is better than the conventional FP-PHP in nearly all of the experimental conditions especially for the optimum filling ratio (50%) in which the thermal resistance was reduced nearly 17%. Furthermore, Flow visualization indicated that additional branches affect the flow regime and enhance flow circulation in PHPs
  9. Keywords:
  10. Pulsating Heat Pipe ; Heat Transfer Enhancement ; Flow Visualization ; Flat-Plate Pulsating Heat Pipe ; Unidirectional Flow ; Flow Circulation

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